1. Field of the Invention
A rehabilitation system that combines robotics and interactive gaming, i.e., visual interaction, to facilitate performance of task-specific, repetitive, ankle, balance and gait-related motor tasks, to enable individuals undergoing rehabilitation from neurological or orthopedic disorders to improve the performance of coordinated movements of the lower limb with special emphasis on the ankle muscles is disclosed. More specifically, the rehabilitation system includes a multiple degree-of-freedom (DOF), robotic ankle component, to assist users in improving or regaining function, strength, full range of motion, and motor control of their ankle(s), and balance trainer component, designed to assist users in retraining standing balance on a stable or moving surface, coordinating lower extremity control with specific ankle movements during uni- or bi-lateral standing activities such as static balance, weight shifting or stepping. Both components (ankle and balance trainer) interface with interactive gaming hardware that is coupled to a computer, to provide a virtual reality-like environment for movement practice.
2. Summary of the Prior Art
Stroke is the leading cause of disability in the United States with approximately 800,000 new cases reported annually, of which about 90,000 die. Typically, there are over 4.5 million stroke survivors in the population at any given time. The physical effects of stroke are variable and may include impairment in motor and sensory systems, language, perception, emotional and cognitive function. Impairment of motor function usually involves paralysis or paresis of the muscles on the side of the body that is contralateral to the side of the brain lesion.
For example, impaired control of gait and dynamic balance are frequent problems with stroke patients. Moreover, the ability to control ankle muscles and produce adequate range of motion in the ankle joints are key components of gait and balance function. Such deficits interfere with overall functional independence and can place patients at an increased risk for falls.
In a recent study of 972 stroke patients receiving in-patient rehabilitation in six facilities in the U.S., the most common treatment activity was gait-related activity. Indeed, more than 50 percent of these sessions involved work on balance and postural awareness. Pre-functional activities were the next most common treatment, and greater than 50 percent of these sessions involved strength training.
The importance of balance control with respect to gait function has been shown in a recent study. The study concluded that balance control is more important in improving walking ability than are improvements in leg strength or muscle synergy control. Other authors have shown that deficits in mobility, muscle strength, and motor control about the ankle joint are key factors that contribute to gait and balance deficits in stroke patients. Although this disclosure will discuss use of the invention by a stroke patient, the invention is applicable to any patient suffering from neurological disorders, including traumatic brain injury (TBI), multiple sclerosis, and Parkinson's disease, or needing to rehabilitate ankle muscles, for example, as a result of orthopedic or sports-related injuries.
Presently, there are no commercially-available devices that are designed for ankle rehabilitation that combine the ability to train balance function, ankle strength, mobility, and motor control into one system, nor do any of the commercially-available devices typically allow use of the device in multiple positions, i.e., standing, sitting, and positions in between. Examples of currently-available devices used for ankle rehabilitation include Wobble Boards, the Ankle Foot Orthosis at University of Delaware (AFOUD), a Robotic Gait Trainer (RGT), a Powered Ankle-Foot Orthosis (PAFO), an Ankle Dorsiflexion/Plantarflexion Exercise Device (ADPED), and the Rutgers Ankle (RA).
Wobble Boards are low cost wooden or plastic platforms to which a rubber semi-sphere is attached to the bottom of the board. Users stand on the board and attempt to balance themselves. Although Wobble boards can be useful for balance training, they are often too difficult for stroke patients to use safely. Furthermore, they do not provide quantitative measurement output that could be used to adjust exercise difficulty and/or to measure patient progress over time.
The AFOUD is a two degree-of-freedom (DOF) ankle device having three links that are connected by two revolute joints corresponding to the three links. The AFOUD can be used as a stand-alone measurement device to measure joint forces and moments applied at both ankle joints.
The RGT, PAFO, and ADPED are devices to assist stroke patients. The RGT is a tripod mechanism that includes a flat plate and two bi-directional actuators that are controlled by a Matlab and Simulink platform. The RGT, however, does not provide a quick response time and its weight and bulkiness do not promote easy wear by stroke patients. The PAFO includes a carbon fiber and polypropylene shell that is wrapped around a patient's leg. A steel hinge joint couples a footplate to the shell. Two artificial pneumatic muscles are controlled by proportional myoelectric control. This robotic exoskeleton device could provide plantarflexion/dorsiflexion (PF/DF) torque at the ankle, but lacks inversion/eversion movement control. The ADPED is another passive motion exercise device for PF/DF movement. However, patients are limited to using this device in a seated position. Furthermore, the RGT, PAFO, and ADPED are designed to provide passive robotic assistance instead of active movement control. They also do not address the balance component of training or comprehensive training of ankle motion and strength control in all planes of movement. Finally, they do not offer an interactive, virtual reality-based (VR-based) interface.
The Rutgers Ankle (RA) incorporates a Stewart platform having six pneumatic pistons working in parallel to create a six-DOF platform. In use, the RA is interfaced with VR software that guides the user's movements and controls the force feedback of the platform. Disadvantageously, the RA can only be operated in a seated position where the thighs are at a 90-degree angle to the torso and the knees are bent at a 90-degree angle. It does not provide balance control training. In addition, it is not commercially available, and would likely be expensive to produce due to its use of expensive sensors and actuators.
The Balance Master was purportedly developed to provide objective assessment and retraining of sensory and voluntary motor control of balance with visual biofeedback. The Balance Master utilizes a fixed, dual-force plate on which a patient stands, to measure the vertical forces exerted by the patient's feet. The center of pressure (COP) of these forces can then be calculated, and used to measure weight shifting and body sway. This is primarily a training device. Another more expensive device produced by the same company, the NEUROCOM uses a force plate that can also be moved (linear translation or angular rotation in the anterior-posterior direction), as well as a visual surround that can be coupled to the force plate movements. This system is designed primarily for diagnosis, especially of vestibular-related balance disorders. The interactive technology and clinically proven protocols allow a clinician/practitioner to objectively and systematically assess sensory and voluntary motor components of balance control.